|Publication number||US3087382 A|
|Publication date||Apr 30, 1963|
|Filing date||Jan 26, 1960|
|Priority date||Jan 26, 1960|
|Publication number||US 3087382 A, US 3087382A, US-A-3087382, US3087382 A, US3087382A|
|Inventors||De Nygorden Per Johan Berggren|
|Original Assignee||De Nygorden Per Johan Berggren|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (10), Referenced by (8), Classifications (8)|
|External Links: USPTO, USPTO Assignment, Espacenet|
April 30, 1963 P. 1, B. DE NYGORDEN 3,037,382
OPTICAL OPAQUE PROJECTION SYSTEMS Filed Jan. 26, 1960 5 Sheets-Shea?l l Fig. Fig.
INVENTOR. Per Johan Berggren de Nygorden.
BY p Wma/1.01 t
April 30, 1963 P. J. B. DE NYGORDEN 3,087,382
OPTICAL OPAQUE PROJECTION SYSTEMS Filed Jan. 26, 1960 5 Sheets-Sheet? l 82h f g Fig]l 1:19.10.
Per lohen Berggren de Nygorden,
l@ c www@ 5 Sheets-Sheet 5 INVENTOR. Per Johan Berggren de Nygorden.
April 30, 1963 P. J, B. DE NYGoRDl-:N
OPTICAL OPAOUE PROJECTION SYSTEMS Filed Jan. 26, 1960 April 30, 1963 P. J. B. DE NYGORDEN OPTICAL OPAQUE PROJECTION SYSTEMS Filed Jan. 26, 1960 5 Sheets-Sheet 4 INVENTOR. Per Johan Berggren de Nygorden April 3o, 1963 P. J. B. DE NYGORDEN OPTICAL OPAQUE PROJECTION SYSTEMS Filed Jan. 26, 1960 5 Sheets-Sheet 5 l El INVENTOR. Per .Johan Berggren de Nygorden.
United States Patent O 3,i37,382 OPTICAL OPAQUE PREECTIN SYSTEMS Per Johan Eerggren de Nygorden, 2965 Decatur Ave., New York, NX. Filed Jan. 26, 1960, Ser. No. 4,634 8 Claims. (El. 819-26) This invention pertains to optical projection systems or apparatus, and particularly to ywhat are known as opaque projectors; that is, for the projection of luminous images from the surfaces of relatively opaque objects. Systems of this opaque projection type are widely used -in industry for the close inspection of either large or small machinery and parts thereof, Iand are also adapted to a variety of other applications, as will be understood by those skilled in the art of optics.
Since the objects or surfaces being imaged by apparatus of this type are almost never characterized by optimum light-deiiection properties, either as to absolute reectivity or as to the contrast range between their parts of high and low relative reflectivity, the principal problem in the held has been that of obtaining a sulciently brilliant and ccntrasty image at the viewing position. inasmuch as projection optics are available for very high eiiiciencies of utilization of the light reflected from the objects being viewed, this problem` in turn has hinged largely on the ability to provide sufficient incident light from the prime source of illumination. Strong-arm methods which attempt to solve this problem merely by the use of brighter and briohter lamps, however, always entail `design compromises or the like which work against the most efficient utilization of the available light, or which involve mechanical or operational drawbacks from the viewpoint of the convenience and comfort of the user.
It is accordingly `a principal object of my present invention to provide a system and apparatus for the opaque projection of object surfaces which will overcome the abovenoted (and other) objections to prior art approaches, by systematically improving the efficiency of utilization ofthe available luminous iiux, both before and after it has irnpinged upon the object, to the end that a total luminous source flux of moderate magnitude will yield `a projected image of adequate brightness. Among other features, for example, my system takes advantage of an arrangement in which the loss of light due to the operation of Lamberts cosine law for reflection, which states that the luminous intensity from a surface element of a diitusely reflecting surface is proportional to the cosine of the angle between the direction of reflection and the perpendicular to the surface, is minimized. In the case of retlection of rays originating from a signicant direction, this law applies equally well to the loss of light due to relatively inclined incidence of the light on the reflecting object, so that the cumulative eiiect of the law (for equal deviations of the incident and reiiected beams `from a perpendicular to the surface) is actually proportional to the square of the cosine of that deviation angle.
I am well aware of the attempts which has been made to eliminate the effect of Lamberts law by providing apparatus, such as a light dividing beam splitter, to permit both the incident and the rellected beams to lie directly upon the perpendicular to the surface element. Such light dividers inherently waste something of the order of onehalf of the incident beam, and one-half of the rellected beam, because of their dividing nature, and these losses being multiplied, the total loss exceeds any possible gain in iinal image brightness due to the achievement of perpendicular incidence and reilection. Moreover, while it is in theory possible to recover a portion of the light flux wasted by the dividing surfaces, such refinements -always complicate the construction and also involve a certain Mice amount of ray dispersion and the like which reduces the final image contrast, and makes the eiiective brightness of the final image, as judged realistically by the user 1n a subjective manner, even less attractive.
In general, I accomplish the main and Subsidiary aims of `the invention by a design and arrangement of the optical parts in such a way that both the angles of incidence and reflection may be maintained as small as possible, consistent with effective utilization of the light, and so that their cosines are as near unity as can practically be accomplished. In addition, I further this principle by dividing the problem of surface illumination of the object into more or less separate regions, so that a plurality, from two up, of actual prime sources of luminous flux are individually `allocated Vto the illumination of spaced but adjacent areas of the object. As will appear from what follows, the arrangement just described permits the use of sources of moderate size and intrinsic brightness to be disposed in an optimum manner from the viewpoint of the cosine-square eliect earlier described; especially where bilaterally symmetrical arrangements of even numbers of such sources are used.
Other objects of the invention are to provide an improved double-wall construction of lamp house adapted especially lfor use with projectors having the main features described above; and to provide a complete opaque projection apparatus well organized into a convenient and eiicient whole for the general purposes mentioned herein.
In order to enable those skilled in this art to understand and to practice my invention without difculty, I will undertake in the following specification to elaborate its principles in connection with certain specific embodiments or constructional examples thereof, but without any purpose to thereby limit the actual scope and spirit of the inventive principles themselves, which are deined in the claims at the end of the specification. These constructional examples -are illustrated in the appended drawings, as follows:
FIGURE 1 is a schematic and diagrammatic illustration of a duplex illuminating system for an opaque projector, including the projection lens and yan indication of the object position.
FIGURE 2; is a top plan view illustrating an actual projector employing the duplex system of FIGURE l.
FIGURE 3 is a vertical sectional View of the apparatus of FIGURE 2, taken along line 3--3 thereof (and of FIGURE 4) and looking in the direction of the arrows.
yFIGURE 4 is a vertical sectional view taken on line 4 4 of FIGURE 3.
FIGURE 5 is a horizontal sectional view, taken on line 5-5 of FIGURE t6, of a further embodiment of the iuvention, using a four-light illuminating system.
FIGURE 6 is a central vertical sectional view thereof, taken on line `6 6 of FIGURE 5, and showing the direction of the imaging rays proceeding to a screen.
FIGURE 7 is a diagram showing the relationship of four individual areas of an object or object-location, separately illuminated by the fou-r light sources of FIGURE 5.
FIGURE 8 is a horizontal sectional view of a further embodiment of the invention, using in this case six symmetrically disposed light sources.
FIGURE 9 is a side elevational view of the same embodiment, showing the housing unit and diagrammatically illustrating the path of the projected image-forming rays.
FIGURE l0 is a diagram, similar to FiGURE 7, showing the relationship amongst the six separately illuminated object regions.
FIGURE ll is a view in end elevation of an arrangement for mounting the optical projection unit to pro-vide an adjustable focal plane' object table and a suitable viewing screen support base.
construction of FIGURE ll, taken on line 12--12 thereof.
FIGURE 13 is an enlarged fragmentary sectional View taken on line 13-13 of FIGURE 11, showing the gear drive and guide parts for the focal plane table.
FIGURE 14 is a top plan view of the complete apparatus including a projector of the type already shown, but to a smaller scale, and mounted on the adjustable screen support table.
FIGURE 15 is a side elevation thereof.
FIGURE 16 is a staggered horizontal sectional View of a modified construction for a six-light projection apparatus, taken on line 16-15 of FIGURE 17.
FIGURE 17 is a central vertical sectional View of the same modification, showing the positions of some of the lamps and condensers, the top image reflector, and lthe' projection lens.
FIGURE 18 is a diagram showing the way in which separate but adjacent illuminated areas are combined in this embodiment to provide a iinal illuminated region at the object.
FIGURE 19 is a top plan view of the complete encased projector of the last embodiment, with its mounting bars.
FIGURE 2O is a side elevational View of FIGURE 19.
FIGURE 21 is a diagram of an optional masking configuration by which the third or central overlap of luminous areas in FIGURE 18 may be moderated in intensity if desired.
`FIGURES l through 4 of the drawings illustrate the application of the novel combination of principles of my invention to a simple form of projector in which only two light sources are employed. Consonant with those principles as already stated, the illumination of a given desired object area is accomplished by breaking it up into parts located on opposite sides of the central perpendicular axis of the whole area, the region on each side being illuminated by the light source or system which also lies on the same side of that perpendicular central axis of the area as a whole. In this way, the total angle between the incident and reflected beams (relative to the object area) is minimized, and thereby the cosine-square loss is also minimized; also, the total object area thus illuminated will more nearly agree with the field of the view of the projection lens, and light waste or spill-over will be reduced.
lIn FIGURE l, reference numeral 26 designates the opaque object whose upper surface, or a selected portion or area thereof, is to be projected with a desired enlargement ratio onto a suitable viewing screen by a projection lens 27. Numerals 22 and 22 designate the two respective prime light sources such as conventional projector lamps, while 23 and 23' indicate the usual condenser lens sets, 24 and 24 indicate the condenser-aperture defining frames or mounts, and 25, 25 designate two separate plane reflectors so angled as to cause the light from each lamp, after collimation by the corresponding condenser,
to fall upon respective halves ofthe object area to be projected. In this way, the angle of incidence of each parallel beam from a lamp is kept as small as possible on the respective side of the central axis of the illuminated area, and the reected beam can readily be accurately directed towards the entrance aperture of projection lens 27 and will stay within the beam acceptance angle of the latter.
The actual physical construction of a projector employing this optical arrangement is fully illustrated in FIG- URES 2, 3 and 4, in which the same parts are designated by the numbers already employed. Viewing screen 28 is placed at the back of an enclosed box or housing 29' having an open front to allow the entrance ofthe projected image, and yalso for direct viewing where the screen is of the front projection type. The projector of these gures was designed specifically'for the problem of presenting a slightly enlarge-d view of type faces (such as used yfor embossing titles on book covers or the like) to enable direct proofreading and inspection thereof; since the type faces themselves are reversed right-to-left, the system is arranged for the necessary inversion to present clear alphabet text letter images for inspection.
Thus, a double reflection in the horizontal plane is necessary to get the letter images right-side-up and in proper reading order. The types 30 are positioned in a movable galley tray or equivalent at 31, and their images are reflected rst at relector 32 and thence at reector 33 before impinging in focussedlcondition on screen 28. The focus position of lens 27 can be adjusted in any known or convenient way, as by sliding, helical or rack-andpinion motion, and a lock screw 34 permits the adjusted position to be maintained as long as wanted for a given installation. The reectors 32 and 33, With their supporting blocks 32', 33', projector lens block 36 and so on, are all mounted within a housing 35 having opening at its front to permit passage of the projected rays to screen 28. A pair of metal side plates 37 and 38 and an end plate 40 support the lens block 36 in position, and the plates 37, 3S are apertured to permit the passage of the beams from the condensers 23, 23. A metal end plate 39 is preferably made removable to enable cleaning of the reflectors 25, 25. These parts are ultimately supported by the door plate 41, carried on channel 42 and aperture'd to pass the rays to and from the type slugs, which may thus, with their carrying tray, be moved forward or back to permit line-by-line inspection of the letters and characters in direct fashion.
The lamps 22 and 22 are preferably mounted in respective sockets as at 43 which are mounted as on washers 44 which also support small reflectors 45 as usual in lamp houses of this type. Thel washers are made movable on brackets such as at Y46, for close positioning of the lampreiiector unit, and locking screws 47 are provided as Well known in the art.
FIGURE 3 also shows in detail an unusual Vform of lamphouse of a nested or double-Wall construction, particularly lapplica-ble to an arrangement such as this in which the operator will be quite close to the lamps and may touch ltheir housings on occasion.
An incandescent projector lamp gets quite hot in service, and will of course raise its enclosing lamp-house to a high temperature. In the present construction, outer larnphouses such as at 48 are provided, and the direct heat rays )from the lamp 22 are prevented Afrom striking this outer shell by a second and inner shell 52, also of metal, and which can thus heat up the outer metal wall only by re-radiation. Large air entrance openings as at 56 far-e provided in floor 41 under each lamphouse, and air entrance ducts yare dened by channels such as at 51 which may also support the main floor 41. 'I'hat is, they may snugly mate with channels k42.
The inner lamphouses 49 are square metal tubes with open lower ends and slianting closed roofs, the side walls hiaving large rectangular openings 52 which permit the rising heated air to vent through large openings `54 in the outer lamphouses 48, along with rising heated air from .between the spaces between the two sets of lamphouse walls. The condensers such las 23 have their rear mounting flanges secured over round openings in front of the lamp filaments, as shown. Each outer lamphouse 48 has an inclined roof or hood 53, and narrow spider brackets 55, 56 support the inner lamphouse in its proper nested position within the outer one.
The principles of the invention as already described can be carried `forward and ampliiied, for apparatus providing 'higher magnications and even better image definition, by multiplying the number of sets of symmetrically disposed illumination sources. FIGURES 5 to 7 illustrate a form in which the number of light sources is doubled, providing :four units designated .by the letters A, B, C and D, of which only one needs to be described in detail, as follows.
Each lamphouse is exactly as already described, including the lamp, its reflector, the provision for adjustment of these two parts as a unit relative to the condensers, and so on. The lamp socket Washers are in this case, however, adjustably positioned directly upon the oor plate 57 which has Ventilating openings as iat 58 and 59 (in pairs) beneath each lamphouse, and the central opening 66 to allow the light to pass to and Ifrom the object surface at 82. In the web of floor material beneath each pair of Ventilating openings, the lamp socket washers are directly mounted for adjustment as described above. The four inner walls of the four lamphouses, at 67, 68, 69* and 70, extend upwardly from floor plate 57 :and are secured to Ian upper cross plate 711 ywhich is fastened to two cross bars 72 and 73. The reflector base 74 is mounted on plate 71, and reflector 75 is carried by this base at the proper angle for directing the reected rays to the screen, not shown.
The combined reiiector and projections lens pyramidal mounting block 76 is joined to t-he four lamphouse walls already mentioned, and the four trapezoidal light reectors 77, 7S, 79 land `80, carried on block '76, pick up and reect the light Vdownward from the lamps to the object at 82. The projection lens S1 gathers the light reilected from the object and forms the image on the screen after reflection at 75. As best illustrated in FIGURE 7, the object area 82 is made up of four partial individual adjacent 4areas a, b, c and d which are illuminated respectively by the four light sources on the respective same sides of the central axis of the equipment.
'Ihe way in which the apparatus just described is incorporated into and supported by a suitable mechanical structure will be described below. First, reference to FIGURES 8 through 10 will clarify the application of the optical principles to a six-light arrangement, directly comparable and analogous to the four-light arrangement except that the rectangular configuration of parts in FIG- URE 5, for example, becomes the hexagonal configuration of six taper-sided lamphouses as seen in the horizontal section of FIGURE 8. In FIGURE 9, numeral 110 indicates the m-ain floor plate, having a central opening as at 123 `for the illuminating and imaging rays passing to and from object area 124. As shown in FIGURE 10, the illuminated object area is in fact made up of six triangular sections e, f, g, h, i and 1'. In these diagrams, it will be understood that the boudaries `are indicated in idealized form, and that some overlap or irregularity can he tolerated in the shapes of the illuminating bea-ms. The reflectors for the beams issuing from the condensers Will here again be trapezoidal, but mounted on six converging faces of la hexagonal pyramid which is truncated across the lens-axis face.
Any of the projector apparatus of the foregoing FIG- URES can advantageously .be mounted :for use in the equipment of FIGURES 11 to 113. Thus, the support bars 72 and 73 of FIGURE 6 occupy the position represented at the bar 73 in FIGURE 11, extending from the fixed upright beam structure 83 on which is movably carried the adjustable focal plane object table 84 attached to a rigid bed 86 having a threaded hole `87 (FIGURE 12) receiving the threaded shaft 88 for raising and lowering, the shaft having at its end thrust Washers l89 and a bearing 9i), and being rotated by miter lgears 92, 93` adjacent the upper shaft bearing 91 and in turn driven by a shaft 94 in bearing 95 :and a hand wheel as `shown at 97, preferably with a knurled-rim wheel 96 for tine adjustment.
To ensure smooth and steady vertical motion, without any side swing of the table 84, the bed plate 86 may have a yoke 98 (FIGURE :12) engaging a guide rod 99, anchored to the vertical beam 83. Also, to prevent any bending of shafts `88 and `9S, a slide guide plate or har 1111 may be placed in beam stru-cture 83 to guide the heel of the bed plate `86. The table 84 lmay have usual left and right and transverse motions under the control of other screws and hand wheels or knobs, as shown. Micrometer dials and position indicating scales may be provided on the parts, 'as required for the particular application in hand.
Since the useful magnication of the projector depends on the distance of the projection screen from the projection lens (the object plane position being adjusted accordingly to follow well-known lens laws), provision is made for a wide range of adjustment of the effective screen distance, as best shown in FIGURES 14 and 15. The equipment already detailed in connection with the description of FIGURE 1l is shown at the right of these gures, similar parts being again marked with the same numerals. As shown, the table or base S5 is a relatively long structures to provide adequate screen distances, and carries a sliding plate `103 in dovetail guides. At its left end, plate 183 mounts an upright support 104 on which screen 192 is fastened. Beneath and secured to plate 103 is a threaded nut element 195 engaging a longitudinal threaded shaft 106 in end bearings 107 and 188 which are secured to the base table. At the projector (rightI hand) end or this shaft a hand wheel 109 is provided, rotation of which enables the operator to make desired changes in the screen distance. Here again, suitable table scales or like position-indicating means may be provided in any convenient or well known manner.
FIGURES 16 to 21 illustrate a modication of the projector illuminating system which can be employed in place of those already described. Instead of employing a partitioned and fully controlled individual illuminating system, wherein each light source almost exactly covers its allocated portion of the total area to be projected, this modifi-cation is a free plural illuminating system providing a degree of overlap as between the regions illuminated by each lamp system. This is made possible, Without departing objectionably from the basic principle of minimiz ing the incidence and reection angles, by using special globular projection lamps 12,5 (six being shown) having very compact concentrated filaments and with about 3A of the superlicial area of each globular lamp envelope covered with silver or reiecting plating, and with a small clear area for the light from the concentrated ilament to pass towards the condensers 126. Thus, there is no intermediate reflection of the light passing from source to object, as in the previous forms of the invention, and the illuminated areas can and will overlap to some extent as indicated at 127 in FIGURE 18.
The lamps are placed in bayonet-type sockets 128 carried on ln'nged mounts 129, making it possible to swing the sockets for convenient replacement of lamps, as indicated in dash lines in FIGURE 17. Each lamp socket hinge is attached to a block 131) fastened to the main floor plate 131. The screws 132 threaded through the plate 131 and/or blocks 13() engage the hinge part and permit precise adjustment of the distance of the lamp lilament from condenser 1126, to provide either collimated, convergent or divergent lbeams of light to illuminate areas 127, with the overlap indicated in the diagram of FIG- URE 18.
Since there is not only the overlap indicated at 127 in FIGURE 18, but a resultant third central overlap as at 150, it may be desired to reduce excessive central area illumination by suitably masking each of the beams at or adjacent the respective condensers 126, as by a mask plate 151 shown in FIGURE 2l, having its segments 152 made opaque at positions nearest the axis of the projector equipment.
The projectoin lens 133 lits within the tapered mounting 134 (FIGURE 17) which is fastened to the upper cover plate 135, and the uper and lower .plates are joined by six outside cover plates 139 screwed thereto, as in FIG- URES 19 and 20. The upper cover plate 135 has six ventillation openings 138, individually covered by hoods 139 attached to the cover plate 135. On the hexagonal extension tube 149 is fastened the cross plate 141 supporting the image reflector mirror 143 on its base 142.
Projector-mounting cross bars 144 and 145 are secured to cross plate 141 and correspond to the support bars 73 of FIGURE l1; that is, they support the Whole projector upon the vertical beam 83. The projector thus described is completely interchangeable with the forms earlier described, insofar as its mounting on the main base and screen support is concerned.
From what has been said above as to the construction of the various forms described herein, it will be clear that the shaping of the illuminating beams, and their posiv tioning to illuminate individually allocated parts of the composite area of the object to be projected, can be effected in various Ways. Thus, it can lbe accomplished by the inherent shaping of the beams by the use of angulated reiiectors lying on the converging lfaces of polygonal pyramidal support blocks, as in FIGURES 5, 6 and FIG- URES 8, 9 of the drawings, or by the use of auxiliary shaping masks as in FIGURES 17 and 21. Hc-Wever, this basic principle, in combination with the structure by which the total angle between the incident and reiiected rays or beams is kept at a minimum, can be accomplished by other devices.
Having described several Ways of carrying my invention into practice, I Wish it to be understood that the details of construction may be varied by those skilled in this art Without departing from the true spirit and scope of my invention, and I therefore do not wish to be limited to the details as shown, except as may be required by the sco-pe of the appended claims.
What is claimed is:
1. Optical projector apparatus for displaying an image of the surface detail of opaque objects, comprising an object support, a projection lens system for projecting onto a viewing screen rays of light from an extended surface of an object on said support, a plurality of objectilluminating light sources disposed at equal distances on opposite sides of the optical axis of said projection lens system and on the same side of said object support as said lens system, and individual object-illuminating beam projector optical systems associated with said light sources and constructed and arranged to direct individual condensed beams of light upon adjacent separate area portions of said extended surface of an opaque object on said object support along respective axes closely bunched about the said optical axis of said projection lens system.
2. Optical projector apparatus for displaying an image of the surface detail of opaque objects, comprising an object support, a projection lens system for projecting onto a viewing screen rays of light from an extended surface of an object on said support, a plurality of objectilluminating light sources disposed at equal distances on opposite sides of the optical axis of said projection lens system and on the same side of said object support as said lens system, and individual object-illuminating beam projector optical systems associated with said light sources and constructed and arranged to direct individual condensed beams of light upon adjacent separate area portions of said extended surface of an opaque object on said object support along respective axes closely hunched about the said optical axis of said projection lens system; each of said object-illuminating systems including beam-shaping means to provide the totality of the illuminating beams with a cross-sectional shape uniformly illuminating a predetermined total area of the opaque object.
3. Optical projector apparatus for displaying an image ofthe surface detail of opaque objects, comprising an object support, a projection lens system for projecting onto a viewing screen rays of light from an extended surface of an object on said support, a plurality of object-illuminating lightY sources disposed at equal distances on oppos ite sides of the optical axis of said projection lens system and on the same side of said object support as said lens system, individual condenser lens systems associated with said light sources to collect their respective luminous rays into condensed beams, and optical means closely encircling the axis of said projection lens system and positioned to direct said beams predominately onto adjacent separate area portions of said extended surface of an opaque object on said object support along directions substantially perpendicular `to the said surfaceof such object.
4. Optical projector apparatus for displaying an image of the surface detail of opaque objects, comprising an object support, a projection lens system for projecting onto a viewing screen rays of light from an extended surface of an object on said support, a plurality of objectillurninatinglight sources disposed at equal distances on opposite sides of the optical axis of said projection lens system and on the same side of said object support as said lens system, individual condenser lens systems associated with said light sources to collect their respective luminous rays into condensed beams, and optical means disposed closely adjacent the axis of said projection lens system and positioned to direct said beams vpredominately onto adjacent separate area portions of said extended surface of an opaque object on said object support along directions substantially perpendicular to the said surface of such object.
5. Apparatus in accordance with claim 4, in which said optical means comprises individual shaped reflectors disposed about said axis and lying substantially on the fiat trapezoidal faces of a pyramid.
6. Apparatus in accordance with claim 5, in which said reflectors are mounted upon a pyramidal block which is truncated perpendicular to its altitude line.
7. Apparatus in accordance with claim 6, in which said projectionlens system is mounted in said block and coaxial with said altitude line.
8. An optical projector apparatus as in claim 2, wherein said beam shaping means comprises a masking plate having opaque segments at positions nearest the optical axis of the projection lens system, to prevent Vany substantial overlapping of the individual object-illuminating beams at their adjacent edges.
References Cited in the iile of this patent UNITED STATES PATENTS 1,127,504 Patterson Feb. 9, 1915 1,489,988 Dickinson Apr. 8, 1924 1,841,063 `Semenitz Ian. 12, 1932 1,887,650 Lamer et al Nov. 15, 1932 2,198,815 Haskin Apr. 30, 1940 2,468,679 Martin Apr. Z6, 1949 2,566,185 Gardner Aug. 28, 1951 2,602,370 Dodin July 8, 1952 2,660,087 Domeshek Nov. 24, 1953 2,875,806 Shuftan Oct. 28, 1958
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|U.S. Classification||353/67, 362/271, 362/238, 362/243, 359/798|